This invention relates to and offers certain improvements over my invention covered under U.S. Pat. No. 4,549,719 granted 10-29-1985.
The invention relates to mechanical amplifying means which may be used in place of previously employed hydraulic jacks and other hydraulic devices which are well-known to the experts in the field and which are capable of performing this task extremely well and with very high efficiencies; that is, very little of the translated work is lost by way of friction. Hydraulic devices fitting the above description are commonly used on tool machinery to position tools, to lift heavy loads such as machinery, for construction equipment and which are also used to close valve plugs against very high pressure differentials of liquid or gaseous media (see my U.S. Pat. No. 4,320,778).
However, one of the disadvantages of such hydraulic means to alter the force/distance relationship is that hydraulic devices are very susceptible to leakage and rams or piston rods have to be very precisely machined to avoid leakage between sliding stem seals especially when one considers the very high (usually on the order of 1,000-3,000 psi) hydraulic fluid pressures involved. Another disadvantage of hydraulic means is the very high coefficient of cubic thermal expansion which is especially troublesome when a valve to be closed handles a hot fluid, or when the precision-positioned machine tool becomes warm while performing work. Such undesirable thermal-expansion can lead to rather large positioning errors.
Certain mechanical amplifying means for actuators known to the state of the art are shown in U.S. Pat. Nos. 2,443,775, 2,395,223, 4,265,141, 4,270,398 and 3,941,362. All these known devices exhibit neither the simplicity nor the high amplifying ratio which can be achieved with my invention. For example, U.S. Pat. No. 3,941,362 uses a right triangle type toggle mechanism which amplifies only 4:1 (see column 2, line 25 of his specifications). Furthermore, there is no adjustment of his mechanism which in turn is very complex, requiring a cam profile and a two-stage amplification.
My invention overcomes these disadvantages by:
a. eliminating the requirement for a hydraulic fluid, not requiring fine surface finishes, sliding stem seals and the potential of a hydraulic leak; and PA1 b. by utilizing all-metal parts in its construction, it is capable of operating over wide temperature ranges without experiencing significant positioning errors due to thermal-expansion problems.
In addition, my mechanical apparatus is very easy to handle, has a very high efficiency (similar to that of hydraulic systems) and can be produced very economically and without great need for precision.
As a result of the above-cited advantages, such mechanical amplifying means are now capable of replacing hydraulic amplifying and positioning means on valves such as the one shown in my U.S. Pat. No. 4,278,234, for example. Additionally, amplifying ratios of more than 15:1 are possible.
More advantages of my invention will become apparent when viewed in light of the following description.